A. Golf Ball Construction and Composition
Most modern golf balls comprise a core and at least one additional outer layer. Two-piece balls include a cover around a solid, often single-piece, spherical rubber core. Two-piece balls have high initial speeds but relatively low spin rates, and hence perform well for drives. Ball performance can be further modified by including additional layers between the core and outer cover layer. A three-piece ball has one additional layer between the core and outer cover layer, a four-piece ball results if two additional layers are introduced between the core and outer cover layer, and so on.
The materials used to make individual golf ball layers also significantly affect both the ability to process compositions, as well as the performance of golf balls made using such compositions. Currently, most golf balls utilize core compositions comprising synthetic rubbers based on polybutadiene, especially cis-1,4-polybutadiene. The properties of the core can be further modified by crosslinking. In addition, the weight and hardness of the core may be further adjusted by incorporating various filler materials. Additional compositions for forming golf balls also are disclosed in assignee's issued patents and copending applications.
B. Particular Known Golf Ball Compositions
Particular polyurethane and polyurea compositions have been used to make golf ball components, such as durable golf ball covers. Composition modifiers and processing aids also have been used with such compositions. For example, U.S. Pat. No. 4,123,061 discloses using an amine-based curing agent. The '061 patent states that:                The polyurethanes which are useful in the practice of the present invention are the urethane prepolymers made from polyethers with diisocyanates. Although any diisocyanate may be employed, the preferred diisocyanates are 2,4 tolylene diisocyanate (TDI), 4,4′ diphenylmethane diisocyanate (MDI), and 3,3′ dimethyl 4,4′ biphenylene diisocyanate (also known as 3,3′ dimethyl 4,4′ biphenyl diisocyanate) (TODI). The polyether part of the prepolymer is preferably a polyalkylene ether glycol having an average molecular weight of less than 1,000 and having from about 4 to about 8 carbon atoms in the alkylene group. Best results have been obtained with polytetramethylene ether glycol. It is preferred that only polyether prepolymers be employed. Most polyester urethane prepolymers are unsatisfactory because of their high hydrolysis constant. When golf balls are made from polyester urethanes they are usually unsatisfactory. It will be understood, however, that a mixture of prepolymers can be employed if desired.        The prepolymer is cured with either a polyol or an amine-type curing agent. The polyol curing agent may be trifunctional or tetrafunctional. It is important to note that the curing agent may not be a difunctional polyol since difunctional polyols do not result in a golf ball which has the advantages of the present invention. Examples of polyol-type curing agents useful in the practice of the present invention are triisopropanol amine (TIPA) and trimethylol propane (TMP). Best results have been obtained with the TMP. As to the amine-type curing agents, there must be at least two amine groups present and best results have been obtained with aromatic diamines. Typical amine-type curing agents which are useful in the practice of the present invention are: 3,3′ dichlorobenzidene; 3,3′ dichloro, 4,4′ diamino diphenyl methane (MOCA); N,N,N′,N′ tetrakis (2-hydroxy propyl)ethylene diamine (sold by Wyandotte under the trade name Quadrol); and Curalon L which is Uniroyal Inc.s' brand name for a mixture of aromatic diamines. A plurality of curing agents may be employed, if desired (emphasis added).U.S. Pat. No. 4,123,061, column 2, line 54 through column 3, line 6.        
Similarly, U.S. Pat. No. 5,334,673 discloses using amine curing agents for making polyurethane compositions. For example, the '673 patent discloses using aromatic curing agents, such as polytetramethyleneoxide-di-p-aminobenzoate. U.S. Pat. No. 5,334,673, Abstract.
U.S. Pat. No. 7,276,570 also discloses a polymeric composition ostensibly useful for producing golf balls. According to the Abstract for the '570 patent, disclosed compositions:                [C]omprise at least one polymer having a plurality of amide linkages and a plurality of anionic moieties attached thereto. These compositions can be used in any one or more portions of the golf balls, such as inner center, core, inner core layer, intermediate core layer, outer core layer, intermediate layer, cover, inner cover layer, intermediate cover layer, and/or outer cover layer.However, as currently understood, the polymeric material disclosed by the '570 patent includes anionic moieties in the polymeric backbone, as opposed to having such moieties bonded to the polymeric backbone and available for further reactions, such as a crosslinking reaction.        
Aromatic amines can cause discoloration of compositions comprising such compounds. For example, U.S. Pat. No. 7,041,769, entitled “Polyurethane Compositions for Golf Balls,” states that “[f]urthermore, because the polyurethanes and polyurea used to make the covers of such golf balls generally contain an aromatic component, e.g., aromatic diisocyanate, polyol or polyamine, they are susceptible to discoloration upon exposure to light, particularly ultraviolet (UV) light.” U.S. Pat. No. 7,041,769, column 2, lines 21-26. The '769 patent discloses forming polycarbonate polyols, e.g., HO—[R—OCOO—]nR—OH.
Despite the previously known compositions used to make golf balls, there still is a need for additional compositions. For example, new compositions would provide additional flexibility in tailoring the physical characteristics of golf balls, would facilitate processing such compositions, or both, and hence still are in demand.